This invention relates to a captive panel fastener assembly, and more particularly to a captive panel fastener assembly particularly suitable for being captivated to panels such as aircraft panels and the like.
Panel fasteners for aircraft cowlings and other aircraft panels are well known in the art. In the customary means of assembly, a stud with an enlarged head is inserted through the opening of the panel and into a nut member attached to the base structure of the aircraft. The stud is then torqued to secure the panel. To prevent the stud from falling out of the panel when removed from the nut and possibly being lost, or falling into a jet engine intake and thereby damaging the engine, the stud is usually coupled with a retaining means which captivates the stud to the panel.
One such captivated panel fastener is shown in U.S. Pat. No. 3,294,140. As seen in this patent, the stud has an enlarged head and three splines extending intermediate its length. A retaining ring formed with integral tabs is snapped over the unsplined leading end of the stud and the tabs placed in the splines. Once in place, the retaining ring and the enlarged head of the stud function as stops to captivate the stud and prevent it from being displaced from the panel. In this embodiment, the retaining ring must be relatively flexible, and the tolerances between the tabs and the spline must be relatively loose to permit the ring to be snapped over the leading end of the stud.
Because of the flexibility of retaining ring and the loose tolerances between the splines and the tabs, it as been found that the stud, particularly if cocked at an angle, can become accidentally detached from the retaining ring and resultantly from the panel. As mentioned above, this has important consequences if the stud cannot be located and the plane is in an inaccessible area, or if the stud were to fall into the jet engine intake and damage the engine.
Therefore, it is an object of this invention to provide a captivated stud retaining ring which will not become displaced after installation.
Another objective of this invention is to provide a captive panel fastener assembly with a stiff retaining ring and a close-fitting relationship between the stud and the retaining ring of the assembly.
A further object of this invention is to provide a captive panel fastener assembly with a retaining ring which can be installed without deforming the ring and without the necessity of special tools.
Still another object of this invention is to provide a captive panel fastener assembly which is economical and feasible to manufacture.
Further objects of the invention will in part be obvious and in part appear hereafter.
The invention comprises a captive panel fastener assembly comprising a stud, retaining ring and end plug. The stud is formed with an enlarged head, three splines extending substantially along its length and a centrally located bore at its forward end. After the stud is inserted into a panel hole, of a diameter smaller than the enlarged head of the stud, tabs of the retaining ring are inserted into the splines of the stud and the end plug is then press-fitted into the stud bore to retain the ring. The stud is thus captivated to the panel. As the retaining ring is relatively rigid and the clearance between the tabs and the splines substantially close, the retaining ring is prevented from "walking" over the leading end of the stud and thereby becoming displaced.